Precast concrete modular construction is a growing industry. In such construction, large, heavy precast concrete sections are molded in a casting mold or bed at a central location. This minimizes the capital investment necessary in the molds and provides good quality control. After the castings are molded, they are lifted from the mold and carried to a storage area until they are needed for the actual construction. At the proper time, the precast concrete castings are moved from the storage area to the construction site where they are assembled into building or other structures.
Over the years, techniques have been developed which facilitate the lifting of the heavy concrete castings from the casting mold or bed. U.S. Pat. No. 4,056,912 to Case et al. discloses a common threaded insert which is molded into the concrete casting. A threaded bolt on a lifting sling can be threaded into this insert to lift the concrete casting from the mold to the storage area, and later from the storage area to the installation site. At installation, the threaded insert is covered over or filled and has no further use.
Various techniques have also been developed for securing one concrete casting to another in the actual building structure. One such technique is disclosed in U.S. Pat. No. 4,627,212 issued to Yee. This patent discloses a splice sleeve which is used to connect reinforcing bar from mating concrete castings using a metallic non-shrink grout. The sleeve is precast in one of the concrete castings. The casting to which it is mated has a portion of reinforcing bar extending from the casting which is then received into the splice sleeve. Subsequently, the reinforcing bar is grouted to the splice sleeve with pressure grouting. This splice sleeve has been found to provide an adequate shear connection between the concrete castings.
The lifting devices of the type disclosed in the Case patent, and the shear connectors such as shown in the Yee patent are completely separate components. This requires the expenditure for both these types of components in each construction job.